Numerous modern-day electrical circuits utilize magnetic core components in accomplishing desired objectives. Audio and alternating current (AC) transformers and inductors typically include iron, powdered iron, or ferrite magnetic substrates. While the precise composition of such substrates varies with respect to design goals, common form structures take the shape of rods, toroids, or pot cores having single or multiple winding coils integral thereto. The windings in conjunction with the magnetic substrate define the operating parameters of the device. Such structures are typically bulky and their physical dimensions often define the minimum size requirement of associated devices or subsystems.
Recently, low-profile substrates have become more popularly known, often taking the form of a flat monolithic substrate with vias or through holes for plated or hard wire windings. One example of such a device may be found in U.S. Pat. No. 5,534,837 issued Jul. 9, 1996 to Randy L. Brandt and incorporated herein by reference. The use of low-profile perforated plates for magnetic core substrates was hampered, in part, due to inaccuracies in modeling the inductance of such devices. Conventional modeling approaches proved inaccurate in view of the non-conventional structure. Although numerous combinations were possible, empirical formulas have been devised and published addressing such modeling issues. One such publication is a paper entitled “Inductance Modeling for a Mode-2 Perforated-Plate Matrix Inductor/Transformer”, by S. Kirli, K. D. T. Ngo, et al, IEEE Annual Power Electronics Specialists Conference 1993, pages 1131-1136.
Power conditioning networks, particularly magnetic components of EMI filters, use one or more inductors to accomplish necessary system objectives. Traditionally, the EMI filter magnetic functionalities are separated into two or more inductors, i.e., the first inductor in conjunction with the circuit bulk capacitance provides the differential mode (DM) filtering functionality, while the second inductor (typically a coupled choke) in conjunction with common mode (CM) capacitance provides the CM filter functionality. In high-power EMI filters, the multiple inductors associated with the conventional approach are large and weighty, and consume significant volume of the power supply containment space.
As power converters and their associated circuits become more complex, it is desirable to be able to reduce the occupied volume and form factor variabilities of the magnetic components. Consequently, there exists a need for low-profile inductors of high reliability and low cost.